Hot or cold food receptacle utilizing a peltier device with air flow temperature control

ABSTRACT

A temperature controlled food storage unit is provided with a Peltier device ( 18 ) to effectuate the temperature of food place in a thermally conductive container or basin ( 24 ). Air from a fan ( 52 ) is passed through an air duct ( 50 ) and over a heat sink ( 22 ), which is thermally coupled to one side of the Peltier device ( 18 ). A hand-operated damper ( 54, 64 ) is used to control the air flow through the air duct ( 50 ) and over the heat sink ( 22 ) thereby controlling heat exchange between the Peltier device ( 18 ) and ambient air.

FIELD OF THE INVENTION

This invention relates to a temperature controlled food storage unitthat uses a solid-state, thermoelectric heat pump device commonly knownas a Peltier device.

BACKGROUND OF THE INVENTION

FIG. 1 is a perspective view of a prior art food storage container 10that provides a cold storage using a solid-state, thermoelectric heatpump device. The types of foods kept in container 10 often include itemssuch as meats, soups, cheeses, vegetables, and condiments, includingcondiment dispensers. Multiple food storage containers 10 of similar orvarying sizes can be used simultaneously in food service preparationcounters or carts, such as used in the assembly of sandwiches andpizzas, and also commonly used in soup and salad buffets.

FIG. 2 is a cross section of the storage container 10 taken along line2-2 of FIG. 1. FIG. 2 depicts the interior walls 14, which are usuallymade from a thermally conductive material such as aluminum or stainlesssteel, and a bottom or base 16, which is also thermally conductive.

A thermoelectric assembly 17 is thermally coupled to the bottom 16 ofthe food container 10. The thermoelectric assembly 17 includes asolid-state, thermoelectric device 18, which is sandwiched between athermal transfer plate 20 and a heat sink 22.

The thermoelectric device 17 is embodied as a Peltier device worksaccording to the Peltier effect. One side of the device will be cool orcold while the opposite side is warm or hot, depending on the directionof current flow through the Peltier device. The Peltier device 18 actsas a heat pump in that heat is absorbed on the cold side and transferredto the hot side where it is dissipated.

In FIG. 2 the Peltier device is configured to have its cool or cold sidefacing the base 16 of the container 10 in order to cool the container. Athermal transfer plate 20, embodied as a block of thermally conductivematerial such as copper or aluminum, is located between and thermallycoupled to both the cold side of the Peltier device 18 and the base 16of container 10.

The Peltier device 18, the cold side of which is against the thermaltransfer plate 20, will absorb heat from the plate 20, causing itstemperature to drop. The heat transfer plate 20 will thereafter absorbheat from the base 16 of the container 10.

A heat transfer medium, such as a silicone thermal transfer grease ortape, is often paced between the Peltier device 18 and the thermaltransfer plate 20 to improve conductive heat transfer between the twobodies. The heat sink grease or tape can also be placed between thethermal transfer plate 20 and the base 16 of the container 10.

In addition to the thermal transfer plate 20, a heat-dissipating sink 22is located below the Peltier device 18 and thermally coupled to the hotside of the Peltier device 18. The heat sink 22 is also comprised ofmaterials having a relatively high thermal conductivity coefficient,such as copper and aluminum. As with the cold side and the thermaltransfer plate 20, thermal transfer grease or tape, can be used betweenthe Peltier device 18 and heat sink 22 to improve heat transfer therebetween.

The structure depicted in FIG. 2 is known prior art, however, a drawbackof prior art food storage devices that use Peltier devices is that thetemperature inside the container is effectuated by controlling thePeltier device electrically. Prior art refrigerators that use Peltierdevices effectuate temperature control by measuring temperatures andshutting off or adjusting current to the Peltier device. Sensingtemperature and controlling electric power requires electronic devicesthat add manufacturing cost and which are themselves subject to failure.A food storage device that uses a solid state Peltier device and whichcan effectuate temperature control without having to rely on sensors andelectronic or electrical control devices would be an improvement overthe prior art.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a prior art food storage container;

FIG. 2 is a cross-section taken along line 2-2 of FIG. 1 of a prior artfood storage container showing the connection of a Peltier device;

FIG. 3 is a perspective view of a food receptacle that can be kept hotor cold by a Peltier device, with the inside temperature of thereceptacle being controlled by air flow over;

FIG. 4 is a cross-sectional view of the device shown in FIG. 3

FIG. 5 is an alternative embodiment of a manually controlled damper formanually controlling air flow over a heat sink of a Peltier deviceconnected to a food storage device;

FIGS. 6A, 6B and 6C is another alternative embodiment of a manuallycontrolled damper for manually control air flow over a heat sink of aPeltier device connected to a food storage device; and

FIGS. 7A, 7B and 7C bottom view showing the use of manually rotatableheat-sink fins for manually controlling air flow over the heat sink of aPeltier device connected to a food storage device.

FIG. 8 shows the use of multiple Peltier devices, thermally coupled inparallel to a food storage container;

FIG. 9 shows the use of stacked Peltier devices connected to a foodstorage device;

DETAILED DESCRIPTION

A known characteristic of Peltier devices is that the heatdissipation/absorption of one side is proportional to the heatabsorption/dissipation from the other side. Stated another way, thetemperature of the cold side is proportional to the heat dissipated fromthe hot side. The hot side temperature is proportional to heat absorbedby the cold side. Depending on which side is thermally coupled to a foodstorage container, a Peltier device can thus be used to either sink heatfrom food receptacles that need to be kept cold or provide heat toreceptacles that need to be kept hot.

Temperature control of Peltier device-cooled food receptacles disclosedherein is effectuated by controlling heat dissipated from the Peltierdevice hot side. Temperature control of Peltier device-heated foodreceptacles disclosed herein is effectuated by controlling the heatabsorbed by the Peltier device cold side.

Heat dissipation from the hot side and heat absorption by the cold sideis controlled by controlling air flow. In one embodiment, air flowcontrol is accomplished by a movable damper located either up stream ordownstream of a fan that moves air across a heat transfer body. Inanother embodiment, air flow control is accomplished by an air flowdiverter that routes air through or around a heat transfer body. Inanother embodiment, air flow control is accomplished by controlling thespeed of a fan that moves air across a heat transfer body. In yetanother embodiment, heat transfer from or heat transfer into a Peltierdevice is accomplished by a finned heat transfer body, the fin structureof which is rotatable relative to the air flow direction such thatrotating the heat sink fin structure parallel to an air currentdirection, increases heat transfer while rotating the heat sink finstructure orthogonal to an air current reduces heat transfer.

FIG. 3 shows a perspective view of a first embodiment of a foodreceptacle 24 (also considered herein to be a container and a basin) thetemperature of which is effectuated by heat transferred through aPeltier device 18. FIG. 4 is a cross-sectional view.

As shown in the figures, the opposing, heat-transferring sides of thePeltier device are thermally coupled to a thermal transfer plate 20 anda heat sink 22, which are spatially and thermally separated from eachother. One side of the thermal transfer plate 20 is thermally coupled tothe bottom 23 of the basin or food storage container 24, which itself ispreferably made from a thermally conductive material suitable for use ina restaurant, food service or kitchen, examples of which includestainless steel or aluminum. The opposite side of the thermal transferplate 20 is thermally coupled to one side of the Peltier device 18. Asdescribed above, the thermal transfer plate 20 effectuates heat transferbetween the Peltier device 18 and the food storage container 24.

An air duct 50 directs air from a fan 52 over the heat sink 22. Theorientation and placement of the fan is a design choice but the fan 52is preferably attached to a side wall of a cabinet, similar to the oneshown in FIG. 1 that supports the food storage container 24. In oneembodiment, the fan 52 is behind a safety grill and can be operated withor without an air filter. The orientation of the fan 52 can be changedso that the fan 52 can be mounted inside the cabinet and draw air froman air space between the bottom of the cabinet and a countertop or flooron which the food storage device is operated.

As explained more fully below, the temperature inside the food storagecontainer is controlled by controlling air flow over the side of thePeltier device that is opposite the food storage container and not bysensing temperature inside the container 24 and/or controlling electricpower to the Peltier device 18. In an alternate embodiment, however, atemperature sensing device can be used to provide for temperaturewarnings or alarms or other operating conditions, such as a thermalrunaway of the Peltier device.

In the embodiment shown in FIG. 3 and FIG. 4, the volumetric flow of theair from the fan 52 across the heat sink 22 is controlled by amanually-operated, i.e., hand-controlled, adjustable damper 54. Thedamper 54 is shown in FIG. 3 as being located away from the fan, i.e.,at the distal or far end 57 of the air duct 50, however, in an alternateembodiment, the damper 54 is located between the heat sink 22 and thefan 52.

The damper in one embodiment is hingedly attached to the duct 50 at thetop 58 of the duct 50. Rotating the damper 54 counterclockwise aroundthe hinge 55, which connects the damper 54 to the duct 50, allowsincreased air flow through the duct 50.

An alternate and equivalent embodiment of the configuration shown inFIG. 3 and 4, but which is not shown uses a damper configured to openwhen it is rotated clockwise. Another embodiment uses a damper 54hingedly attached to the bottom 59 of the duct. One such alternateembodiment uses a damper 54 that opens to allow air through the duct 50when rotated clockwise while another embodiment uses a damper 54 thatopens to allow air through the duct when it is rotated counterclockwise.In yet another embodiment not shown, the duct 54 is embodied as asliding door able to move across the duct in directions that are intoand out of the plane of the paper on which the figure is drawn or, upand down.

Different damper 54 positions between fully open and fully closed willallow correspondingly more or less air from the fan 52 to pass throughthe duct 50 and over the heat sink 22. Heat transfer between the ambientair driven through the duct 50 by the fan 52 will increase when thedamper is “open” and decrease as the damper 54 closes. Changing oradjusting the position of the damper 54 between fully open and fullyclose thus effectively provides heat transfer control of the Peltierdevice, which in turn provides control over the temperature of theopposite side of the Peltier device, i.e., the side of the Peltierdevice 18 facing the food storage receptacle 24 and as a result, thetemperature inside the food storage container 24. Temperature control ofthe receptacle 24 is thus effectuated simply, reliably and mechanically,i.e., by controlling air flow over a heat sink coupled to the Peltierdevice.

FIG. 5. shows an alternate and equivalent embodiment of aduct/fan/damper configuration that can be used to control thetemperature of a food receptacle by controlling air flow. In FIG. 5, thefan 52 is configured to pull or draw air across the heat sink 22 fromair duct 50 whereas in the embodiment shown in FIG. 3 and FIG. 4 the fan52 pushes air through the duct and over the heat sink.

Unlike the embodiment shown in FIGS. 3 and 4, the embodiment of FIG. 5provides maximum air flow across the heat sink 22 when the manuallycontrolled damper 54 is fully “closed,” which is when the damper 54 isrotated in the counterclockwise direction. When the damper 54 is closed,all of the air drawn by the fan 52 is pulled down the duct 50 and acrossthe heat sink 22. As the damper 54 rotates clockwise, it “opens” andallows ambient, room air to flow around or by-pass the heat sink 22. Asthe duct is rotated to is full open position, almost no air is drawnover the heat sink 22.

The embodiment of FIGS. 3 and 4 controls air flow across the heat sink22 by restricting air flow through the duct 50. The embodiment of FIG. 5controls air flow across the heat sink by routing air flow across theheat sink or around the heat sink. Unlike the embodiment of FIGS. 3 and4, the embodiment of FIG. 4 moves substantially the same volume of airthrough the fan 22 at all times. Air flow noise in the embodiment shownin FIG. 5 can therefore be maintained at a more-constant level

FIGS. 6A, 6B and 6C show yet another duct/fan/damper configuration bywhich the temperature of a food storage receptacle 24 using a Peltierdevice 18 can be simply and effectively controlled by controlling airflow. The embodiment shown in FIGS. 6A, 6B and 6C uses a sliding damper64, which in FIGS. 6A, 6B and 6C, is downstream from a fan 52. Inanother embodiment, the sliding damper 64 is at the distal end 57 of theduct, i.e., downstream from the Peltier device 18.

When the damper 64 in FIG. 6C is manually positioned to close offopening 66, the fan 52 will move air through only the opening 62 intothe room, which will prevent air from moving through the duct 50 andover the heat sink 22. When the damper 64 is manually positioned toclose off opening 62 to the room, as shown in FIG. 6A, the fan 52 willmove air through only the air duct 50, which then forces fan air overthe heat sink 22. When the damper 64 is positioned at some intermediateopening position as shown in FIG. 6B, some air will flow through boththe opening 62 to the room and through the opening 64 into the duct 50.Changing the position of the damper 64 will therefore change the amountof air flowing over the heat sink 22. Changing the position of thedamper 64 will thus change the temperature of the side of the Peltierdevice that is thermally coupled to the food storage container 24through the thermal transfer plate 20.

FIGS. 7A, 7B and 7C depict a bottom view of a rotatable heat sink 70,looking upwardly toward the bottom of the food storage container. InFIGS. 7A, 7B and 7C, the orientation of the heat sink relative to theair flow direction controls heat transfer into or out of one side of aPeltier device 18. The temperature inside the food storage container 24is thus controlled by the heat sink 70 orientation. As with theembodiments described above, in FIGS. 7A, 7B and 7C, one side of thePeltier device 18 is thermally coupled a heat transfer plate while theother side is thermally coupled to the finned heat sink 70, which ismade up of multiple generally planar fins 72.

In FIG. 7A, the heat sink 70 fins 72 are substantially parallel to thedirection of the air flow from the fan 52. Air from the fan will tend totravel freely between the fins 72. As the heat sink 70 is rotated asshown in FIG. 7B, the angle between the heat sink fins 72 and the airflow direction will tend to reduce the amount of air flowing through thefins 72, reducing the heat transfer between the air and the heat sink70. As the angle between the fins 72 and the air flow directionapproaches ninety degrees or perpendicular, as shown in FIG. 7C, heattransfer between the heat sink 70 and the air from the fan will beminimized.

Another embodiment of the invention controls air flow over a heat sinkby a variable speed fan and without using any sort of damper or flowcontrol. As used herein, variable speed includes fans using motorshaving speeds that are continuously variable as well as fans usingmotors that operate at two or more different speeds.

Finally, another embodiment controls air flow over a heat sink and as aresult, the temperature inside a food storage container by usingfixed-speed fan motors but using differently-pitched or variably pitchedfan blades.

It is important to note that for all of the embodiments depicted in thefigures and described above, heat transfer direction can be either intoor out of the air stream. The food storage container can thus be eitherhot or cold, depending upon the orientation of the Peltier devicevis-à-vis the food storage container.

When the Peltier device is used to cool the food storage container, thecold side of the Peltier device(s) will face the food storage container.Heat from the food storage container will flow into the Peltier devicecold side and be transferred by the device to its hot side, causing thetemperature of the heat sink 22 to rise. Heat transfer will therefore beout of the heat sink 22 and into the air stream provided by the fan.

When the Peltier device is used to heat the food storage container, heattransfer is reversed in that heat will be absorbed by the cold side ofthe Peltier device from the heat sink 22, conducted through the Peltierdevice and conducted into the food storage container. When the Peltierdevice is used to heat foods, heat is conducted into the heat sink 22and into the Peltier device. The claims should therefore be construed toread on both hot and cold food storage devices, the temperature of whichis effected by one or more Peltier devices.

For purposes of claim construction, the fans, ducts, dampers, fan bladesand movable and adjustable heat sink fins should all be considered airflow control mechanisms because each them is able to control the amountor volume of air flowing over a heat sink that transfers heat from orinto a Peltier device. Since each of them can effectuate or determineair flow and as a result, hence heat transfer between ambient air andthe heat sink coupled to the one or more Peltier devices, each of themcan determine the temperature inside a food storage container. Statedanother way, the temperature control of the food storage containerdisclosed herein is provided essentially by the devices that move and/orcontrol the movement of air over the heat sink. The aforementioned airflow control mechanisms can therefore be also be considered to betemperature control mechanisms as well.

As used herein, the term “heat sink” should not be construed to belimited to a device that absorbs heat from a hot body and whichdissipates heat to the environment. As used herein, “heat sink” shouldbe construed to include a heat transfer body that can either transferheat from a Peltier device, as happens when a Peltier device is coolinga food storage container, and which can transfer heat into a Peltierdevice, as happens when a Peltier device is heating a food storagecontainer. As used herein, a heat sink is therefore thermallybi-directional.

As used herein, the term “duct” should be broadly construed to includepipes, tubes and channels as well as any component or structural elementof a food storage device or cabinet, which routes or directs air fromthe fan 22 over a heat sink. A duct can therefore also include one ormore walls of a multi-wall cabinet, such as a cabinet depicted in FIGS.1 and 2, which supports a thermally conductive basin for storing orholding hot or cold food.

It is also important to note that the temperature control methodologyand structures disclosed herein require adjustment of the various airflow control devices. Stated another way, the damper settings canrequire some experimentation in order to determine a damper settingwhereat a desired temperature is achieved. It is important to also notethat the thermal efficiency of the Peltier device will depend on theambient temperature. Damper settings can require adjustment as roomtemperatures vary.

Those of ordinary skill in the art will also appreciate that the coolingand heating capacity of a Peltier device is limited. Additional heatingand cooling capacity is achieved by operating multiple Peltier devices18, 28 and 38 thermally in parallel with each other as shown in FIG. 8.Each of the devices 18, 28 and 38 has its cold side (or hot side)coupled to the food storage container 24 with its hot side (or coldside) in the controlled air stream provided by the structures describedabove.

Those of ordinary skill in the art will also appreciate that thetemperature differential between the hot side and the cold side of aPeltier device 18 is somewhat limited. Greater temperaturedifferentials, hotter and colder temperatures, can be achieved bystacking two or more Peltier devices 18, 28 and 38 thermally (notelectrically) in series with each other such that the cold side of afirst device is coupled to the hot side of second device. In FIG. 9,three Peltier devices 18, 28 and 38 are stacked in series. The cold sideof a first device 18 is coupled to the hot side of a second device 28.The cold side of the second device 28 is coupled to the hot side of athird device 38. The cold side of the third device 38 is thermallycoupled to a heat transfer plate 20.

In view of the foregoing, the terms Peltier device and solid state heatpump should be construed to include one Peltier device but to alsoinclude multiple devices, whether they are thermally in series with eachother or thermally in parallel with each other.

The foregoing description and various embodiments are to be consideredin all respects as illustrative and not restrictive. The scope of theinvention is determined by the appended claims rather than by theforegoing description.

1. A temperature controlled food storage unit comprised of: a thermallyconductive food storage container (container) for storing food; a solidstate heat pump having a first side thermally coupled to the foodstorage container and a second side coupled to a heat sink; and an airflow control mechanism, directing air over the heat sink; wherebytemperature of the container is determined by the air flow controlmechanism.
 2. The temperature controlled food storage unit of claim 1,wherein the solid state heat pump is a Peltier device.
 3. Thetemperature controlled food storage unit of claim 1, wherein the airflow control mechanism is comprised of an air duct and an adjustabledamper for the duct.
 4. The temperature controlled food storage unit ofclaim 3, wherein the adjustable damper is hand-operated.
 5. Thetemperature controlled food storage unit of claim 1, wherein the airflow control mechanism is comprised of a fan.
 6. The temperaturecontrolled food storage unit of claim 5, wherein the fan is a variablespeed fan.
 7. The temperature controlled food storage unit of claim 1,wherein the solid state heat pump is comprised of a Peltier devicehaving a cold side thermally coupled to the food storage container. 8.The temperature controlled food storage unit of claim 1, wherein thesolid state heat pump is comprised of a Peltier device having a hot sidethermally coupled to the food storage container.
 9. The temperaturecontrolled food storage unit of claim of claim 2, wherein the solidstate heat pump is comprised of a plurality of Peltier devices, the coldsides of which are coupled to the food storage container in parallel,the hot sides of which are thermally coupled to said air flow controlmechanism.
 10. The temperature controlled food storage unit of claim ofclaim 2, wherein the solid state heat pump is comprised of a pluralityof Peltier devices, the hot sides of which are thermally coupled to saidfood storage container in parallel, the cold sides of which arethermally coupled to said air flow control mechanism.
 12. Thetemperature controlled food storage unit of claim of claim 2, whereinthe solid state heat pump is comprised of a plurality of Peltierdevices, thermally coupled to each other in series.
 13. The temperaturecontrolled food storage unit of claim 1 wherein the air flow controlmechanism includes a fan directing air toward said heat sink, andwherein the heat sink is comprised of rotatable fins, the orientation ofwhich is adjustable relative to the direction of air flow from said fan.14. A food storage unit comprised of: a cabinet; a thermally conductivefood storage basin (basin) in said cabinet; a Peltier device having acold side thermally coupled to the basin and a hot side thermallycoupled to a heat sink; a fan; and an air flow control mechanism;whereby basin temperature is determined by said air flow controlmechanism.
 15. The food heating unit of claim 14, wherein the cabinethas at least one side wall and wherein said air flow control mechanismis a damper mounted to said at least one side wall.
 16. The food heatingunit of claim 14, wherein said cabinet is configured to direct air fromsaid fan over said heat sink.
 17. The food heating unit of claim 14,wherein said fan is comprised of a variable speed motor.
 18. The foodheating unit of claim 15, wherein the damper is hand-operated.
 19. Thefood heating unit of claim 12, wherein the air flow control mechanismincludes a heat sink comprised of fins, the orientation of which isadjustable relative to the direction of air flow from said fan.
 20. Atemperature controlled food storage device, comprising: a thermallyconductive receptacle (receptacle) configured to receive a food itemtherein; a thermoelectric device having first and second portion, thefirst portion thermally coupled to and transferring heat energy betweenthe receptacle and the thermoelectric device, effectuating thetemperature of at least a portion of the receptacle; a heat sinkthermally coupled to the second portion of the thermoelectric device,the heat sink configured to transfer heat energy between thethermoelectric device and ambient air driven over surfaces of the heatsink by a fan; and a manually operated air flow control mechanismcontrolling the amount of air conveyed over the heat energy transferdevice by said fan; whereby the temperature inside the receptacle isdetermined by said manually operated flow control mechanism.
 21. Thetemperature controlled device as recited in claim 20, wherein themanually operated air flow control mechanism includes at least one of: adamper manually positionable to inhibit the conveyance of air over theheat energy transfer device; a diverter diverting air flow around theheat energy transfer device; a variable speed fan; and a manuallyadjusted heat sink fin, adjustable between a first and a secondposition, such that when in the first position the fin permits theconveyance of air over the heat sink and when in the second positioninhibits the conveyance of air over the heat sink.
 22. The temperaturecontrolled food storage device as recited in claim 1, further includinga plurality of thermoelectric devices thermally coupled to said foodstorage container.
 23. The temperature controlled food storage device asrecited in claim 12, further including a plurality of thermoelectricdevices thermally coupled to said food storage basin.
 24. Thetemperature controlled food storage device as recited in claim 18,further including a plurality of thermoelectric devices coupled to saidreceptacle.
 25. A temperature controlled food storage unit comprised of:a thermally conductive food storage container for storing food; a solidstate heat pump having a first side thermally coupled to the foodstorage container and a second side coupled to a heat sink; and a foodstorage container temperature control mechanism, the temperature controlmechanism consisting essentially of: an air flow control mechanism,directing air over the heat sink.
 26. The temperature controlled foodstorage unit of claim 25, wherein the air flow control mechanism iscomprised of an adjustable damper for a duct.
 27. The temperaturecontrolled food storage unit of claim 25, wherein the air flow controlmechanism is comprised of is comprised of a variable speed fan.
 28. Thetemperature controlled food storage unit of claim of claim 25, whereinthe solid state heat pump is comprised of a plurality of Peltierdevices, the cold sides of which are thermally coupled to said foodstorage container in parallel, the hot sides of which are thermallycoupled to said air flow control mechanism.
 29. The temperaturecontrolled food storage unit of claim 25 wherein the air flow controlmechanism includes a fan directing air toward said heat sink, andwherein the heat sink is comprised of fins, the orientation of which isadjustable relative to the direction of air flow from said fan.